📘 Class 12 Physics - JEE & NEET Chapter-wise Preparation Guide
1. Electrostatics
🔍 Key Concepts:
- Coulomb’s Law
- Electric Field & Electric Potential
- Gauss’s Law
- Capacitance and Capacitors
🧮 Important Formulas:
F = (1 / 4πε₀) * (q₁q₂ / r²)
E = F/q or E = (1 / 4πε₀) * (q / r²)
V = (1 / 4πε₀) * (q / r)
C = Q / V
⭐ Important Questions:
Derive electric field due to infinite line charge using Gauss's Law.
Two charges +3μC and -2μC are placed 5 cm apart. Find the force.
F = 9×10⁹ * (3×10⁻⁶)(2×10⁻⁶) / (0.05)² = 21.6 N
Capacitance of 1 m² plate area and 0.01 m separation?
C = ε₀A/d = 8.85×10⁻¹² * 1 / 0.01 = 8.85×10⁻¹⁰ F
2. Current Electricity
🔍 Key Concepts:
- Ohm's Law and Resistance
- Kirchhoff’s Laws
- Series & Parallel Combination
- EMF and Internal Resistance
🧮 Important Formulas:
V = IR
P = VI = I²R = V²/R
R = ρL/A
⭐ Important Questions:
Apply Kirchhoff’s Law to a mixed circuit.
Find resistance: L=2m, A=1mm², ρ=1.7×10⁻⁸ Ωm.
R = ρL/A = 1.7×10⁻⁸ * 2 / 1×10⁻⁶ = 0.034 Ω
Cell 2V, r=0.5Ω, external R=3.5Ω → Find current.
I = E / (R + r) = 2 / 4 = 0.5 A
3. Magnetic Effects of Current
🔍 Key Concepts:
- Biot–Savart Law
- Field due to Current-Carrying Wire
- Lorentz Force
- Charged Particles in Fields
🧮 Important Formulas:
B = μ₀I / (2πr)
F = qvB sinθ
F = ILB sinθ
⭐ Important Questions:
Field at center of 10cm coil with 5A current?
B = μ₀I / 2R = 4π×10⁻⁷ * 5 / (2*0.1) ≈ 3.14×10⁻⁵ T
Proton in 0.1T field, v = 10⁶ m/s → Force?
F = qvB = 1.6×10⁻¹⁹ * 10⁶ * 0.1 = 1.6×10⁻¹⁴ N
4. Electromagnetic Induction
🔍 Key Concepts:
- Faraday’s and Lenz’s Law
- Induced EMF & Current
- Self & Mutual Inductance
🧮 Important Formulas:
ε = - dΦ/dt
Φ = B·A·cosθ
E = ½LI²
⭐ Important Questions:
Coil: A=0.05m², ΔB=0.3T, Δt=0.1s → EMF?
ε = ΔΦ/Δt = (0.3 * 0.05) / 0.1 = 0.15 V
State and explain Lenz's Law with example.
5. Optics
🔍 Key Concepts:
- Reflection, Refraction
- Lens & Mirror Formula
- Interference & Diffraction
🧮 Important Formulas:
Lens: 1/f = 1/v - 1/u
Mirror: 1/f = 1/v + 1/u
Magnification: m = v/u
⭐ Important Questions:
Convex lens: f=10cm, u=20cm → Find v
v = uf / (u + f) = 200 / 30 = 6.67 cm
Define interference, give condition for constructive interference.
6. Modern Physics
🔍 Key Concepts:
- Photoelectric Effect
- Einstein’s Equation
- Bohr Model & Nuclear Physics
🧮 Important Formulas:
E = hf = hc/λ
λ = h / mv
⭐ Important Questions:
Energy of photon with λ = 400nm?
E ≈ 6.63×10⁻³⁴ × 3×10⁸ / 400×10⁻⁹ ≈ 4.97×10⁻¹⁹ J
Explain Einstein’s Photoelectric Equation: Ek = hf - φ